The inadequate treatment of municipal solid waste which is being put in landfills and the increasing addition of nondegradable materials, including plastics, to the municipal solid waste streams are combining to reduce drastically the number of landfills available and to increase the costs of municipal solid waste disposal. While the recycling of reusable components of the waste stream is desirable in many instances, there are some products which do not readily fit into this framework, e.g. disposable personal absorbents such as diapers and sanitary napkins, garbage bags, and numerous other products. The composting of non-recyclable solid waste is a recognized and growing method of reducing solid waste volume for landfilling and/or making a useful product from the waste to improve the fertility of fields and gardens. One of the limitations to marketing such compost is the visible contamination by undegraded plastic such as film and fiber fragments.
One object of this invention is to provide components which are useful in disposable products and which are degraded into less contaminating forms under the conditions typically existing in waste composting processes. These conditions may involve temperatures no higher than 70.degree. C., averaging more nearly 55.degree.-60.degree. C., 100% relative humidity and exposure times which range from two weeks to more than three months.
Another object of this invention is to provide disposable components which will not only degrade aerobically in composting, but will continue to degrade in the soil or landfill anaerobically. As long as water is present, they will continue to break down into molecular weight fragments which can be ultimately biodegraded by anaerobic microorganisms completely into biogas, biomass and liquid leachate, as for natural organics like wood.
Other objects of the invention include the provision of novel polyesters for making the aforementioned fibers, films, coatings and nonwoven sheets of the polyesters, and disposable diapers containing the nonwoven sheets.
Still other objects of the invention are to provide polyesters and derivative products which have low ingredient costs and yet provide strength and toughness properties adequate for end uses such as in disposable diapers.